U.S. patent number 11,456,259 [Application Number 16/814,961] was granted by the patent office on 2022-09-27 for panel level packaging for devices.
This patent grant is currently assigned to PYXIS CF PTE. LTD.. The grantee listed for this patent is PYXIS CF PTE. LTD.. Invention is credited to Amlan Sen.
United States Patent |
11,456,259 |
Sen |
September 27, 2022 |
Panel level packaging for devices
Abstract
Panel level packaging (PLP) with high accuracy and high
scalability is disclosed. The PLP employs an alignment carrier with
a low coefficient of expansion which is configured with die regions
having local die alignment marks. For example, local die alignment
marks are provided for each die attach region. Depending on the
size of the panel, it may be segmented into blocks, each with die
regions with local die alignment marks. In addition, a block
includes an alignment die region configured for attaching an
alignment die. Linear and non-linear positional errors are reduced
due to local die alignment marks and alignment dies. The use of
local die alignment marks and alignment dies results in increase
yields as well as scaling, thereby improving throughput and
decreasing overall costs.
Inventors: |
Sen; Amlan (Singapore,
SG) |
Applicant: |
Name |
City |
State |
Country |
Type |
PYXIS CF PTE. LTD. |
Singapore |
N/A |
SG |
|
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Assignee: |
PYXIS CF PTE. LTD. (Singapore,
SG)
|
Family
ID: |
1000006582606 |
Appl.
No.: |
16/814,961 |
Filed: |
March 10, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200312780 A1 |
Oct 1, 2020 |
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Foreign Application Priority Data
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Mar 27, 2019 [SG] |
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10201902757X |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/67144 (20130101); H01L 22/20 (20130101); H01L
23/49838 (20130101); H01L 21/681 (20130101); H01L
21/4853 (20130101); H01L 23/544 (20130101); H01L
2223/54426 (20130101) |
Current International
Class: |
H01L
23/544 (20060101); H01L 21/66 (20060101); H01L
21/48 (20060101); H01L 23/498 (20060101); H01L
21/67 (20060101); H01L 21/68 (20060101) |
Field of
Search: |
;438/5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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201814819 |
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Apr 2018 |
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TW |
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2017/169953 |
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Oct 2017 |
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WO |
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Primary Examiner: Vu; Vu A
Attorney, Agent or Firm: Javalon Law, PC
Claims
What is claimed is:
1. An alignment system for a die bonder comprising: an integrated
camera module configured to view downwards in a vertical direction
towards an active surface of an alignment carrier when mounted on
the die bonder, the integrated camera module comprising a light
source which is configured to emit a light having a wavelength for
penetrating through an adhesive layer disposed on the active
surface of the alignment carrier to enable the integrated camera
module to detect local alignment marks of a die bond region of
interest on the active surface of the alignment carrier with die
bond regions having local alignment marks, and to view upwards in
the vertical direction for viewing a bottom surface of a die when
attached to a bond head of the die bonder for die bonding; and an
alignment controller, wherein the alignment controller is
configured to receive input from the camera module, the alignment
controller is configured to align the die when attached to the bond
head to the die bond region of interest for die bonding based on
the input from the camera module in accordance with the local
alignment marks of the die bond region of interest.
2. The alignment system of claim 1 wherein the alignment controller
is configured to facilitate aligning the bond head in position for
die bonding on the die bond region of interest when the die is
attached to the bond head, wherein aligning the bond head includes
movement horizontally and angularly in a x-y plane based on the
input from the camera module.
3. The alignment system of claim 1 wherein the alignment controller
is configured to move the bond head into an alignment position,
wherein moving the bond head into the alignment position includes
horizontal movement in x and y directions for coarse alignment of
the die when the die is attached to the bond head and angular
movement of the bond head to rotate the die angularly in a x-y
plane for fine alignment to a die attach region of the die bond
region of interest on the alignment carrier.
4. The alignment system of claim 1 wherein the camera module
comprises: a first camera subunit comprising a first collinear
vision camera with a first light source, the first light source
serving as the light source configured to emit the light having the
wavelength for penetrating through the adhesive layer disposed on
the active surface of the alignment carrier, wherein the first
camera subunit is configured to view downwards in the vertical
direction for detecting the local alignment marks on the alignment
carrier; and a second camera subunit comprising a second collinear
vision camera with a second light source, wherein the second camera
subunit is configured to view upwards in the vertical direction for
viewing the bottom surface of the die when attached to the bond
head of the die bonder.
5. The alignment system of claim 4 wherein the second light source
is configured to generate a second light having a second wavelength
sufficient to penetrate the adhesive layer on the alignment carrier
for die bonding to detect the local alignment marks on the
alignment carrier.
6. The alignment system of claim 4 wherein the first and second
camera subunits are disposed side-by-side along a horizontal x-y
plane to reduce a height to reduce a distance traveled by the bond
head with the die to the die bond region of interest for die
bonding.
7. The alignment system of claim 1, further comprising a gantry
assembly configured to position the bond head at successive die
bonding regions on the alignment carrier.
8. The alignment system of claim 7, wherein: the gantry assembly
comprises a support alignment assembly; and the support alignment
assembly further comprises an x-axis actuator, a y-axis actuator,
an angular (.theta.) actuator or a combination thereof for aligning
the bond head in an x-y plane.
9. The alignment system of claim 1, further comprising a bonding
assembly actuator coupled to the bond head for moving the bond head
in a z-direction vertically towards or away from the alignment
carrier.
10. The alignment system of claim 9, wherein the bond head further
comprises a bonding head actuator and a bonding tool, the bonding
head actuator is coupled to the bonding assembly actuator for
controlling the bonding tool to pick up or release the die.
11. The alignment system of claim 1, wherein the light emitted from
the light source has a wavelength of about 600 nm to penetrate the
adhesive layer.
12. The alignment system of claim 4, further comprising: a first
reflector coupled to the first light source for reflecting a first
light emitted from the first light source to a prism which further
reflects the first light downwards to the alignment carrier; and a
second reflector coupled to the second light source for reflecting
a second light emitted from the second light source to the prism
which further reflects the second light upwards to the die.
13. A method for die bonding comprising: providing an alignment
carrier comprising die bond regions defined on an active surface of
the alignment carrier, and local alignment marks on the active
surface for each die bond region, wherein the local alignment marks
facilitate local alignment of bonding to the die bond regions;
mounting the alignment carrier onto a base assembly of a die
bonder; picking up a first die for die bonding onto a first die
bond region on the alignment carrier by a bond head of the die
bonder; aligning the first die to the first die bond region
according to the local alignment marks of the first die bond
region, the aligning the first die to the first die bond region
comprising using an alignment system which is configured to view
downwards in a vertical direction for detecting the local alignment
marks of the first die bond region, and to view upwards in the
vertical direction for viewing a bottom surface of the first die;
sending information of the alignment system to a controller,
wherein the controller aligns the first die to the first die bond
region based on the information from the alignment system according
to the local alignment marks of the first die bond region; and
moving the first die downwards vertically by the bond head to the
alignment carrier after alignment of the first die to the first die
bond region is achieved to bond the first die on the first die bond
region of the alignment carrier.
14. The method for die bonding of claim 13, further comprising
programming the controller to detect the first die bond region to
be an alignment die position or a live die position for determining
the first die to be an alignment die or a live die.
15. The method for die bonding of claim 13, wherein sending
information of the alignment system further comprises sending
carrier alignment points in a carrier CAD file and die alignment
points in a die CAD file to facilitate alignment.
16. The method for die bonding of claim 15, further comprising
matching a die region pattern from the carrier CAD file and a die
pattern from the die CAD file.
17. The method for die bonding of claim 13, further comprising:
segmenting the die bond regions on the alignment carrier into at
least two blocks; bonding a plurality of dies to the die bond
regions in a selected block of the at least two blocks, wherein
bonding the plurality of dies of the selected block comprises
picking up a selected die for die bonding onto a selected die bond
region of the selected block, aligning the selected die to the
selected die bond region according to the local alignment marks of
the selected die bond region, the aligning the selected die to the
selected die bond region comprising using an alignment system which
is configured to view downwards in a vertical direction for
detecting the local alignment marks of the selected die bond
region, and to view upwards in the vertical direction for viewing a
bottom surface of the selected die, sending information of the
alignment system to the controller, wherein the controller aligns
the selected die to the selected die bond region based on the
information from the alignment system according to the local
alignment marks of the selected die bond region, and moving the
selected die downwards vertically by the bond head to the alignment
carrier after alignment of the selected die to the selected die
bond region to bond the selected die on the selected die bond
region of the selected block, determining if there are more die
bond regions in the selected blocks to bond dies to, if there are
more die bond regions to bond dies to, selecting a next die bond
region to be the selected die bond region, and picking up a next
die as the selected die, and repeating the aligning the selected
die, sending information to the controller and moving the selected
die downwards for bonding to the selected die bond region until all
die bond regions of the selected block are bonded with dies, if
there are no more dies to bond to the selected block, determining
if there are more blocks of the at least two blocks to bond dies
to, and if there are, select a next block of the plurality of
blocks as the selected block to bond dies to, and repeat bonding
the plurality of dies to the selected block until die bonding for
all blocks of the at least two blocks are completed.
18. The method for die bonding of claim 17, further comprising
determining whether bonding the dies to the die bond regions in a
first block is completed before moving the bond head of the die
bonder to a second block.
19. The method for die bonding of claim 17, wherein sending
information of the alignment system further comprises sending
information of the at least two blocks to the controller.
20. The method for die bonding of claim 19, further comprising:
identifying the first block according to the information of the at
least two blocks; and identifying a starting die bond region among
the die bond regions in the first block for initializing the die
bonding.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of S.G. Provisional Application
No. 10201902757X filed on Mar. 27, 2019, the disclosure of which is
herein incorporated by reference in their entireties for all
purposes.
FIELD OF THE INVENTION
The present disclosure relates to packaging of devices. In
particular, the present disclosure relates to alignment carriers
and an alignment system having a camera module configured for
aligning dies or devices on the alignment carrier for die
bonding.
BACKGROUND
Panel level packaging (PLP) of devices have garnered significant
interest in recent years. This is due to the larger volume of dies
which can be packaged in parallel compared to conventional wafer
level or substrate level packaging techniques. PLP involves
attaching individual dies on a large carrier for die bonding. For
example, the dies are arranged in a matrix on the carrier, with
rows and columns of dies. The panel, depending on its size, can
accommodate significantly more dies than on a wafer, for example, 3
times to 5 times or more dies than a wafer. This increases
packaging throughput as well as reducing costs.
An important consideration in PLP is the precise positioning of the
die on the panel prior to bonding at a target location.
Conventionally, bonding locations are calculated based on global
reference marks on the panel and each die is placed in a
predetermined position by precise mechanical movement of a bonding
head.
However, conventional PLP techniques suffer from positioning errors
on the carrier. Positioning errors may occur due to various
reasons, such as geometry related issues (e.g., straightness,
linearity, and orthogonality), temperature issues (e.g., expansion
of scales, slides, and distortion) and vibration issues (e.g.,
high-speed motion over long distances may result in stopping
position errors). In addition, during the reconstruction or
reconstitution process, the carrier and panel (dies with molding)
undergo thermal cycles of expansion and contraction. Additional
thermal cycles may be experienced due to reuse of the carriers.
Panel distortion causes geometry or size to vary from the original
design from which the die locations are calculated. The more
thermal cycles experienced, the greater the distortion. The
distortion problem is further exacerbated as the panel size
increases. Distortion causes displacement of dies on the panel from
the original calculated locations. Displacement of dies negatively
affects the yield of the bonding process, increasing costs. The
greater the distortion, the greater the displacement. The greater
the displacement, the greater the negative effects on yields and
costs. Due to the displacement errors, subsequent processes involve
significant error mitigation to construct the circuits more
accurately
From the foregoing discussion, it is desirable to provide PLP with
high accuracy throughout the bonding process to increase yields as
well as to improve scalability.
SUMMARY
Embodiments of the present disclosure generally relate to devices.
In particular, the present disclosure relates to die bonding using
an alignment carrier. The alignment carrier may be employed for die
bonding of single die packages or multiple die packages, such as
multi-chip modules (MCMs). The die bonding is facilitated by a die
bonding tool with a camera or an alignment module configured to
align dies for bonding onto the alignment carrier.
In one embodiment, a device includes an alignment carrier for die
bonding which includes a planar carrier and die bond regions
defined on the planar carrier. Each die bond region of the planar
carrier includes local alignment marks for use in die bonding.
In one embodiment, an alignment system for a die bonder includes an
integrated camera module configured to view downward in a vertical
direction for detecting local alignment marks of a die bond region
of interest of an alignment carrier with die bond regions having
local alignment marks when the alignment carrier is mounted on a
base assembly of the die bonder. The integrated camera module is
further configured to view upwards in the vertical direction for
viewing a bottom surface of a die when attached to a bond head of
the die bonder for die bonding. The system further includes an
alignment controller for receiving input from the camera module,
the alignment controller is configured to align the die when
attached to the bond head to the die bond region of interest for
die bonding based on the input from the camera module.
In one embodiment, a method for die bonding includes providing an
alignment carrier including die bond regions defined thereon. The
die bond regions include local alignment marks to facilitate
aligning dies for die bonding of the dies to the die bond regions
and the alignment carrier is mounted onto a base assembly of a die
bonder. The method further includes picking up a first die for die
bonding onto a first die bond region on the alignment carrier by a
bond head of the die bonder and aligning the first die to the first
die bond region using an alignment system. The alignment system is
configured to view downward in a vertical direction for detecting
local alignment marks of the first die bond region, and to view
upwards in the vertical direction for viewing a bottom surface of
the first die. The method further includes sending information of
the alignment system to a controller which aligns the first die to
the first die bond region based on the information from the
alignment system. The method continues to include moving the first
die downwards vertically by the bond head to the alignment carrier
after alignment of the first die to the first die bond region is
achieved to bond the first die on the first die bond region of the
alignment carrier.
These and other advantages and features of the embodiments herein
disclosed, will become apparent through reference to the following
description and the accompanying drawings. Furthermore, it is to be
understood that the features of the various embodiments described
herein are not mutually exclusive and can exist in various
combinations and permutations.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and form part
of the specification in which like numerals designate like parts,
illustrate preferred embodiments of the present disclosure and,
together with thy: description, serve to explain the principles of
various embodiments of the present disclosure.
FIG. 1 shows various views of a semiconductor wafer;
FIG. 2 shows a simplified top view of an embodiment of an alignment
carrier for die bonding;
FIG. 3 shows an embodiment of a process flow for preparing an
alignment carrier for die bonding;
FIG. 4 shows a simplified side view of an embodiment of a bonding
tool;
FIGS. 5a-b show simplified top and side views of an embodiment of a
camera unit of the bonding tool;
FIG. 5c shows an exemplary distance configurations of components of
the camera unit;
FIG. 6 shows a portion of another embodiment of an alignment
carrier;
FIGS. 7a-b show an exemplary die layout of a die bond region with
multiple dies;
FIGS. 8a-f show a simplified process for attaching a die onto a die
bond region of an alignment carrier;
FIG. 9 shows a simplified flow for die bonding using an alignment
carrier;
FIGS. 10a-d show an embodiment of an alignment process in greater
detail;
FIGS. 11a-f show simplified cross-sectional views of an embodiment
of a reconstruction process of dies using an alignment carrier;
FIGS. 12a-c show a process for die location check on a carrier
substrate;
FIG. 12d shows an example of a DLC export file;
FIG. 12e shows calculated saw lines of the panel assembly from
DLC;
FIGS. 13a-e show simplified cross-sectional views of an embodiment
of downstream processing of dies on a carrier substrate; and
FIGS. 14a-b show simplified side and top views of trace
interconnect tolerance with respect to bond contacts of the
downstream processing using the alignment carrier with local die
alignment marks and alignment dies.
DETAILED DESCRIPTION
Embodiments generally relate to devices, for example, semiconductor
devices or integrated circuits (ICs). In particular, the present
disclosure relates to die bonding of devices using an alignment
carrier. The alignment carrier may be employed for die bonding of
single die packages or multiple die packages, such as multi-chip
modules (MCMs). The die bonding is facilitated by a die bonding
tool with a camera or an alignment module configured to align dies
for bonding onto the alignment carrier.
FIG. 1 shows simplified views of a semiconductor wafer 100. For
example, a top view 100a and side views 100b-c of the wafer are
shown. The wafer may be a lightly doped p-type silicon wafer. Other
types of wafers may also be employed. A plurality of devices 105
are formed on an active surface of the wafer. For example, the
active surface may be the top surface of the wafer while the
inactive surface may be the bottom surface. The devices are
arranged in rows along a first (x) direction and columns along a
second (y) direction. After processing of the wafer is completed,
the wafer is diced along the dicing lines 120 in the x and y
directions to singulate the devices into individual dies 105, as
indicated by the side view 100c.
Processed wafers may be incoming processed wafers from an external
supplier. For example, a packaging vendor may receive the processed
wafers. The processed wafers may be diced into individual dies for
packaging using alignment carriers and die bonding tools fitted
with alignment modules to align dies for die bonding onto the
alignment carriers.
FIG. 2 shows a simplified top view of an embodiment of an alignment
carrier 200. The alignment carrier is configured for die bonding,
such as attaching dies thereto. As shown, the alignment carrier is
a rectangular-shaped carrier. Other shaped carriers may also be
useful. In a preferred embodiment, the panel is formed of a
material having a low coefficient of expansion (CTE) to minimize
linear variation during temperature changes. The panel, for
example, may be formed of a material having a CTE at or below 8.
Furthermore, the material should be robust enough to withstand the
handling during the bonding process. In addition, the material
should preferably be magnetic, enabling the panel to be held firmly
during grinding processes which are part of the overall bonding
process. For example, the low CTE material may include, for
example, Alloy 42 (CTE3-4.5) and Alloy 46 (CTE7-8). Other types of
low CTE materials may also be used to form the alignment carrier.
Forming the alignment carrier using other materials as well as
materials with other CTEs, including those having a CTE above 8 may
also be useful. The size of the alignment carrier may be as large
as 600*600 mm. Providing alignment carriers having other sizes may
also be useful.
The alignment carrier, in one embodiment, includes die bonding
regions 240. A die bonding region is configured to accommodate a
die for die bonding. For example, each die bonding region of the
alignment carrier is configured to accommodate a die for die
bonding. In one embodiment, a die bonding region includes local
alignment marks 250 for aligning a die to a die attach region 252.
For example, each die region includes its own local die alignment
marks for attaching a die thereto. The die attach region is the
region of the die bond region on which the die is attached.
In one embodiment, a die bond region includes at least two local
die alignment marks. Providing other numbers of local die alignment
marks greater than two may also be useful. For example, the die
region may include 2-4 alignment marks. Providing other numbers of
alignment marks, including more than four alignment marks may also
be useful. As shown, the die region includes 4 local die alignment
marks. The local die alignment marks, for example, are located on
the corners of the die bond region, forming corners of a rectangle.
Other configurations of the local die alignment marks may also be
useful.
The alignment marks, in one embodiment, are preferably located
outside of the die attach region. For example, the alignment marks,
as shown, surround the die attach region. Providing alignment marks
which are within the die attach region or a combination of
alignment marks outside and within the die attach region may also
be useful. Providing the alignment marks outside of the die attach
region advantageously facilities post bonding inspection, if
necessary. The die bond region may be configured to accommodate a
single die or multiple dies, such as a multi-chip module (MCM)
application. In the case of an MCM application, providing alignment
marks outside the die attach region advantageously enables an
alignment mark to serve as a common alignment mark for bonding
multiple dies onto the die bond region. If alignment marks are
disposed within the die attach region of one of the dies,
additional alignment marks may be provided for die bonding of other
dies of the MCM.
In one embodiment, the local die alignment marks are configured for
detection by a collinear vision camera for alignment. The local die
alignment marks may be formed on the die bond regions of the
alignment carrier using, for example, laser drilling. Other
techniques for forming the local die alignment marks may also be
useful. Preferably, the local die alignment marks are shallow
alignment marks which facilitate removal by grinding for recycling
of the panel. For example, local alignment marks may be removed and
new ones are formed for die bonding of another or different type of
die, such as when a die is no longer in production.
Providing local die alignment marks for each die bond region
improves the positional accuracy of die bonding for each die bond
region, as compared to calculating die bond positions based on
global alignment marks, as is conventionally done. Furthermore, by
providing local die alignment marks, effects of panel distortion or
other positioning errors are minimized, improving positional
accuracy of dies on the alignment carrier, thereby improving yield
and scalability.
The die bond regions of the alignment carrier may be configured in
a matrix format, with rows and columns of die bond regions in first
and second directions. For example, the die bond regions 240 are
arranged in a matrix format, each configured to accommodate a die.
The alignment carrier may include at least two designated alignment
die bond regions 245. For example, the alignment carrier may
include 2-4 alignment die bond regions. Providing other numbers of
alignment die bond regions may also be useful. The alignment die
bond regions may be located at corners of the matrix of die bond
regions. Other configurations of alignment die bond regions may
also be employed.
An alignment die region is similar to other die regions of the
panel, except that an alignment die bond region is designated for
an alignment die. For example, an alignment die is die bonded to an
alignment die bond region. An alignment die may be a normal or live
die, such as dies bonded in the other die bond regions of the
carrier. Live or normal dies are packaged and sold to customers and
into products. For example, an alignment die may be a live die
which is also used for alignment purposes.
In other cases, an alignment die may be specifically configured for
alignment purposes. Providing specific alignment dies may be
advantageous as they can be easily distinguished from normal or
live dies. In such cases, alignment dies are not for normal use.
Preferably, the top of an alignment die is processed with features
which are easily detectable by the alignment camera. This produces
contrast in the alignment image, making it easy to detect. Other
types of alignment dies are also useful. Alignment dies may be
processed on the same wafer as the normal dies or on different
wafers.
In one embodiment, the alignment carrier may be divided or
segmented into die bond region blocks 220. The blocks, for example,
are distinct blocks, with a space separating adjacent blocks. In
some embodiments, the blocks may not be distinct blocks. For
example, the die bond regions may be divided into blocks which are
not separated by spaces. For example, the blocks may appear to be a
continuous matrix of die bond regions.
A block is configured to accommodate a plurality of dies for die
bonding. Segmenting the panel into blocks is advantageous as this
segments the panel into smaller dimension blocks to reduce
displacement errors caused by large panels. For example, the blocks
provide a large panel with the advantage of scale while retaining
the advantages from smaller sized panels. As shown, the panel is
divided into 4 panel blocks. Dividing the panel into other numbers
of blocks may also be useful. For a 600*600 mm alignment carrier,
the blocks may be about 270*270 mm. Preferably, the blocks are
configured to be the same size blocks. Other numbers of blocks and
block sizes may also be useful. The number of blocks and block
sizes may depend on different factors, such as material, size of
the panel, and process conditions. The size of the block should be
selected to effect high processing yields while maintaining the
advantage of scale.
A block, in one embodiment, includes at least one alignment die
bond region 245 for bonding an alignment die thereto. Providing
more than one alignment die bond regions may also be useful. For
example, a block may include 1-4 or more alignment die regions. An
alignment die bond region may preferably be disposed at a corner
position of the block. For example, alignment die bond regions may
be disposed at the 4 corners of the block or 1-3 corners of the
blocks. Locating alignment die bond regions at other positions of
the block may also be useful. The more alignment die regions there
are, the more accurate the die bonding process. However, it may be
at the cost of a lower number of die outputs per alignment carrier,
in the case where alignment dies are specifically for alignment
purposes, since more die regions are assigned to alignment dies. In
some embodiments, adjacent blocks may share alignment die bond
regions. For example, in the case where a block is provided with
one alignment die bond region, it can share a second alignment die
region from an adjacent block. Other configurations of sharing
alignment die regions between blocks may also be useful.
An alignment die serves as a further reference point for each
block. Providing blocks with alignment dies enables linear and
non-linear errors occurring in downstream processes, such as
molding, to be reduced to fractions. For example, linear and
non-linear positioning errors are reduced significantly. In
addition, the alignment die serves as an origin reference for each
die within a block.
As described, the alignment carrier is formed of a metallic
material with local alignment marks. The use of a metallic material
is advantageous as it allows a magnetic table to be used to hold
the carrier firmly in place for processing. For example, a magnetic
table may be employed to firmly hold the carrier in place for
grinding the mold compound.
In other embodiments, the alignment carrier may be formed of glass
or other types of transparent material. The local alignment marks
may be formed on the transparent carrier. In other cases, the local
alignment marks may be independent of a transparent carrier, such
as a glass carrier. For example, local alignment marks may be
formed on a separate mark sheet, such as paper or resin, and may be
attached to the bottom or inactive surface of the transparent
carrier. The adoption of the independent local marks eliminates the
need for the marking process on the panel, and thus reduces
manufacturing cost significantly Light from a camera module of a
die bonder can penetrate through the transparent carrier to detect
the local alignment marks on the mark sheet. The adoption of the
independent local marks can be achieved easily and eliminates the
need for the marking process on the carrier. Furthermore, providing
local alignment marks independent of a transparent carrier is
advantageous since it avoids the need to mass-produce glass panels
with local alignment marks. This can result in significant savings
since glass panels are fragile and the marking process is
expensive.
FIG. 3 shows an embodiment of a process 300 for preparing an
alignment carrier for die bonding. At 310, a base alignment carrier
is provided. As discussed, the base alignment carrier may be a low
CTE alignment carrier. For example, the alignment carrier may be
formed of Alloy 42 (CTE3-4.5) or Alloy 46 (CTE7-8). Other types of
low CTE materials may also be used to form the alignment carrier.
At 320, the surface of the panel is prepared. For example, the
bonding or active surface of the alignment carrier is prepared. In
one embodiment, the surface preparation includes grinding to ensure
flatness and thickness uniformity as well as a scratch-free
surface. In some cases, the active surface may be treated to
further harden the surface to prevent it from being scratched as
well as from being discolored. As for the non-bonding or inactive
surface, it may be grounded to ensure that it is free of dents and
burrs.
Proceeding to 330, the process continues to form alignment marks on
the active surface of the panel. The alignment marks are formed
with high precision to get an accurate pitch from mark to mark. For
example, alignment marks are formed in virtual die regions on the
active surface of the panel. The die regions may be configured into
separate virtual blocks. The pattern of the marks may be based on
the panel layout of a panel computer-aided design (CAD) file. The
alignment marks, for example, may be formed using laser, mechanical
drilling or etching. Other techniques for forming the marks may
also be useful.
After the alignment marks are formed, an adhesive tape is applied
on the active surface of the alignment carrier at 340. The tape is
applied on the active surface of the alignment carrier in
preparation for die bonding. For example, the tape covers the
active surface, including the local alignment marks and die
regions. The tape, in one embodiment, is a thermal release tape.
Other types of tapes may also be used to facilitate die bonding.
The tape should be sufficiently transparent to enable an alignment
unit of a bond module with cameras to detect the alignment marks
for aligning the die to the alignment carrier. For example, the
tape may be semi-transparent to enable the light of the alignment
unit to penetrate through the tape to detect the local alignment
marks. In one embodiment, the cameras of the alignment unit are
configured to image the alignment marks on the alignment carrier
vertically downwards as well as upwards to image the bonding
surface of the die for accurate bonding of the die to the die
bonding region of the alignment carrier. In addition, the
stickiness of the tape should be strong enough to hold the dies in
position once aligned and placed thereon by a bonding tool. After
applying the tape, the alignment carrier is ready for die
bonding.
FIG. 4 shows a simplified diagram of an embodiment of a die bonder
400. As shown, the die bonder includes a base assembly 420 for
supporting an alignment carrier 410. For example, the base assembly
is configured to hold an alignment carrier 410 for bonding. The die
bonder includes a bonding assembly 430 mounted on a support or
gantry assembly 435. The bonding assembly, for example, is
positioned above the base assembly. The bonding assembly includes a
bonding head 441 and a bonding assembly actuator 440. The bonding
assembly actuator is configured to move the bonding head in a
z-direction (vertical direction) towards or away from the alignment
carrier. The bonding head includes a bonding head actuator 444 and
a bonding tool (bonder) 442. The bonding head actuator controls the
bonder to pick up or release a die.
The support or gantry assembly is configured for actuating the
bonding assembly to position the bonding head at successive die
bonding regions on the alignment carrier. For example, the support
assembly includes a support alignment assembly which is configured
to align the bonding head in an x-y plane for positioning the
bonding head at successive die bonding regions for die bonding. For
example, the support alignment assembly may perform coarse
alignment of the bonding head to the die bonding region for die
bonding. After the coarse alignment, the support alignment assembly
performs fine alignment of the bonding head to bond the die to the
die attach region. Coarse alignment may include moving the bonding
head in the x and/or y directions to the die bonding region while
fine alignment may include moving the bonding head in the x and/or
y directions as well as rotating the die along the x-y plane by the
die bonding tool.
In one embodiment, the support alignment assembly includes an
x-axis actuator, a y-axis actuator, and an angular (.theta.)
actuator for performing the planar motion along the horizontal x-y
plane and/or angular motion about an axis of the bonding head to
facilitate course and fine alignments. The coarse and fine
alignment may be performed continuously or discontinuously. For
example, continuous coarse and fine alignments may be in the case
when they are both performed after picking up a die by the bonding
head from a feeder assembly (not shown); discontinuous coarse and
fine alignment may be when course alignment is performed prior to
picking up the die by the bonding head and fine alignment is
performed afterwards.
To facilitate alignment of the die to the die bonding region, the
bonding assembly includes an integrated camera module 450. For
example, the camera unit extends to image the die region on the
alignment carrier and the die on the bonder 442 of the bonding head
441. Coarse alignment may be performed with the use of the camera
module or without. For example, positions of the die bonding
regions may be roughly or coarsely determined based on an alignment
die bonding region or position. Alternatively, coarse alignment may
be determined by using the camera module. As for fine alignment, it
is facilitated by the camera module.
The camera unit includes cameras and light sources for emitting
light for image capturing. The light sources, for example, are
capable of emitting light that can penetrate through the adhesive
layer on the panel to identify local die alignment marks by the
camera module to align a die to the die attach region of the die
bonding region by moving the bond head. For example, the light
source or sources may generate light having a wavelength of about
600 nm to penetrate the adhesive tape. Other wavelengths which may
penetrate the adhesive tape may also be useful. In one embodiment,
the camera module includes a lookdown camera for viewing the
alignment carrier.
The light also enables the camera module to view the die on the
bonding head, enabling alignment of the die to the die attach
region by rotating the die in the x-y plane. For example, the
camera captures the image of the target location as well as an
image of the die. In one embodiment, the camera module includes a
lookup camera for viewing the die panel. A die bonder controller
computes the offset values with respect to the target location in
the x and y directions as well as the angle in the x-y plane. Once
calculated, the controller adjusts the bonding head accordingly for
placement of the die on the target die attach region.
The present system can accommodate attaching a die on the die
carrier using the active or non-active surface. For example, the
die can be attached to the alignment carrier in a face-up or
face-down configuration. Face up, for example, refers to the
inactive surface of the die being attached to the alignment carrier
while face down refers to the active surface of the die being
attached to the alignment carrier. For face-down configurations, a
transparent layer, such as ABF, may be applied on the active
surface of the die. This enables the camera module to further
utilize features on the die to serve as alignment features. For
example, the lookup camera may view the features of the active
surface of the die to serve as alignment marks. In some cases, an
inactive surface of the die may be processed to include alignment
features for the lookup camera to detect. By using the lookup
camera, the die bonder can improve accuracy by adopting a cluster
of multiple features on the bottom or bonding surface of the
die.
As discussed, the die bonder is configured with one bonding
assembly with a die bonding head. To increase throughput, the die
bonder may be configured with multiple die bonding assemblies
mounted onto a support assembly. For example, the die bonder may be
configured with 4 or 6 bonding assemblies for die bonding multiple
dies in parallel on an alignment carrier. In some cases, multiple
alignment carriers may be die bonded in parallel using multiple
bonding assemblies. The individual bonding assemblies may be
configured to operate independently of each other. For example,
each bonding assembly includes its respective support assembly and
camera module for independent alignment of the die to the die
attach region.
Also as described, the support alignment assembly performs both
coarse and fine alignments. In some embodiments, the base assembly
may include a translatable table for performing coarse alignment of
the carrier while the support alignment assembly performs fine
alignment. Other configurations of aligning the bonding head to the
bonding region on the alignment carrier may also be employed.
FIGS. 5a-b show different simplified views of a camera unit 500.
For example, FIG. 5a shows a top view of the camera unit while FIG.
5b shows a side view of the camera unit. The side view of the
camera unit shown in FIG. 5b, for example, may be viewed from the
front or from the x direction.
Referring to the FIGS. 5a-b, the camera unit includes first and
second integrated alignment camera subunits 530a-530b. The
integrated camera subunits are high resolution collinear camera
subunits, one for viewing the alignment carrier 510 and the other
for viewing the die 514. For example, the first camera subunit
(lookdown) 530a is configured to view or image the alignment
carrier while the second camera subunit (lookup) 530b is configured
to view or image the die in an optical deflector subunit 540. As
shown, the camera subunits are disposed side-by-side in the x-y
plane. An integrated camera subunit includes a collinear camera
(534a or 534b) coupled to a high-resolution lens (536a or 536b). A
light source (538a or 538b) is configured to emit light capable of
penetrating the adhesive tape covering the alignment marks on the
panel. For example, the light source may generate light at a
wavelength of 600 nm. Other wavelengths which are sufficient to
penetrate the adhesive tape or transparent dielectric layer may
also be useful.
The light is passed to the reflector subunit 540. The reflector
subunit is configured to reflect light from the first light source
538a via a first reflector or mirror 542a to a prism 546 which
further reflects the light from the first light source downwards to
the panel (lookdown camera), while the light from the second light
source 538b is reflected from the second reflector or mirror 542b
to the prism 546 and further upwards to the die (lookup camera).
This enables the camera unit to capture images from both the die
and die attach region on the carrier, giving it a direct line of
sight for alignment.
As discussed, the camera module utilizes simultaneous recognition
of the die and local alignment marks on the alignment carrier using
lookup and lookdown cameras. The ability to simultaneously
recognize both local alignment marks on the alignment carrier and
the die imparts high accuracy in die bonding. Furthermore, by
configuring the cameras of the camera unit in the x-y plane
(horizontal plane or side-by-side), the integrated camera module is
a compact module in the z or vertical direction. This
advantageously decreases the movement of the bond head to the panel
along the vertical distance between the bond head and the alignment
carrier, enhancing throughput.
FIG. 5c shows an exemplary configuration of distances 501 of
components of the camera unit. For example, distances of the lens
to prism, the prism surface to mirror surface, the mirror surface
to prism surface, the prism surface to prism surface, the prism
surface to mirror surface, the mirror surface to prism surface, the
prism surface to ring glass, the glass surface to glass surface,
and the prism surface to panel are shown. The units of the
distances are in millimeters (mm). The distances include actual
distance and distance in air. The camera unit may include other
distance configurations for the components.
FIG. 6 shows a simplified diagram of a portion of an embodiment of
an alignment carrier 610. The alignment carrier includes a
plurality of die bond regions 640 arranged in a matrix format. The
die bond regions may be separated into blocks of die bond regions.
Surrounding a die region are local die alignment marks 650. For
example, four local alignment marks are provided for each die bond
region, surrounding corners of the die attach region. Providing
other numbers of local alignment marks as well as other
configurations of local alignment marks may also be useful.
In one embodiment, a die attach region is configured to attach
multiple dies. For example, as shown, a die attach region includes
first and second die attach regions configured for attaching first
and second dies 614.sub.1 and 614.sub.2. Attaching other numbers of
dies to a die attach region may also be useful. The multiple dies
of the die region are attached using the same local die alignment
marks. Using the same local die alignment marks ensures relative
accurate positioning of the dies on the die attach regions.
Furthermore, using the same local die alignment marks enables
accurate die positioning for interconnections between dies, such as
high annular ring tolerance. In addition, using the same alignment
marks eliminates errors due to hole positions. For example, if
separate alignment marks are used for positioning the multiple
dies, then the error due to the hole position may be added to the
positional error between the dies.
As described, the local alignment marks are disposed outside of the
die attach regions of the die bond region. This is advantageous
since, as already discussed, this enables the same local die
alignment marks to be used for attaching the dies. However, in some
cases, the alignment marks may be disposed within the die attach
regions. In such cases, each die attach region of the die bond
region may need respective sets of local alignment marks. In other
cases, there may be a combination of alignment marks within and
outside of a die attach region of a die bond region. It is
understood that various configurations of local alignment marks for
the die attach regions of the die bond region may be employed.
FIGS. 7a-b show embodiments of multiple dies attached to a die
attach region using the same local die alignment marks. FIG. 7a
illustrates a configuration for attaching first and second dies
714.sub.1 and 714.sub.2 on a die attach region 740 using the same
local die alignment marks. As shown, the first die may be an AP die
formed using 14 nm technology while the second die may be a BB die
formed using 28 nm technology. As for FIG. 7b, it illustrates a
configuration for attaching dies 714.sub.1-714.sub.5. As shown, the
dies include an AP die formed using 14 nm technology, a BB die
formed using 28 nm technology, a power management integrated
circuit (PMIC) die, an integrated passive device (IPD) die and a
radio frequency (RF) die. Other configurations of multiple dies on
a die attach region may also be useful.
As described, the alignment carrier may be employed for packaging
MCMs. For example, dies of different types with different functions
can be packaged into a single packaging structure using the present
alignment carrier with local alignment marks and bonding assembly.
Accurate alignment can be achieved for MCMs using the alignment
carrier and die bonder.
Bonding different types of dies on the alignment carrier may be
achieved using various techniques. In one embodiment, separate die
bonders may be employed for bonding the different types of dies on
the carrier. For example, a first die bonder is employed to bond a
first type of die of the MCM on the alignment carrier. After
bonding of the first type of dies onto the alignment carrier is
completed, the carrier is transferred to a second die bonder for
bonding the second type of die of the MCM onto the carrier. This
process may be repeated until all types of dies of the MCM are
bonded onto the carrier, one type of die after another. In another
embodiment, the same die bonder may be employed to bond the
different types of dies of the MCM onto the carrier. For example,
after completion of bonding the first type of dies of the MCM onto
the carrier, the die bonder is reprogrammed to bond the second type
of die. The process is repeated until all types of dies are bonded
onto the alignment carrier. The use of local alignment marks in MCM
applications advantageously enables different dies to be bonded by
different die bonders while still maintaining the same base
reference and relative accuracy. This is not possible with
conventional techniques, such as those using global alignment
marks.
FIGS. 8a-8f show simplified diagrams depicting an embodiment of a
process 800 for die bonding on an alignment carrier. Referring to
FIG. 8a, a die bonder 802, such as that described in, for example,
FIGS. 4 and 5a-5b, is shown. An alignment carrier or panel 810 is
disposed on the base assembly 820. A support alignment assembly may
align the bonding head to the die bonding region on the carrier.
For example, coarse alignment of the bonding head 842 to the
carrier is performed. A die feeder assembly 860 feeds a die 814 to
the bonding head. For example, the die feeder extends under the
bond head.
Referring to FIG. 8b, the bonder picks up the die 814 from the
feeder 860. For example, the bonding assembly actuator 840
positions the bond head 842 on top of the die and the bonding head
actuator actuates the bonder of the bond head to pick up the die.
The bonder may employ vacuum pressure to pick up the die from the
die feeder. After the die is picked up, the die feeder is retracted
away, exposing the die attach region on the carrier on which the
die is to be attached. It is understood that the coarse alignment
of the alignment carrier can be performed after die pickup.
In FIG. 8c, the camera module 850 is extended for alignment. For
example, the camera module is extended into position for fine
alignment. Fine alignment includes positioning the bonding head so
that the die is aligned to the die attach region, both in the x and
y directions and also rotationally.
As shown in FIG. 8d, after fine alignment of the die to the die
attach region is achieved, the camera module 850 is retracted,
exposing the die attach region on the carrier 810. In FIG. 8e, the
bonding assembly is actuated to move the bonding head vertically to
attach the die to the die attach region on the alignment carrier.
After the die is attached, the process continues to attach a next
die, as shown in FIG. 8f. For example, the bonding head is
translated to the next die attach region stage on the carrier 820
and the die feeder 860 provides another die 816 to the die bonder.
The process repeats by aligning and attaching the die to the die
attach region until all die attach regions on the carrier are
bonded with dies. Furthermore, the controller of the system is
programmed to know whether an alignment die or a live die is to be
supplied to the bonding tool, based on which die region on the
panel for bonding.
As previously discussed, the die bonder may be configured with a
translated base assembly to perform coarse alignment while the
support alignment assembly performs fine alignment. In addition,
alignment dies may be the same as a live die or specifically for
alignment purposes.
FIG. 9 shows an embodiment of a process flow 900 for die bonding
using an alignment carrier. The bonding process starts at 905.
Initialization may be performed at 910. Initialization may include
information regarding the bonding process. For example, the size of
the carrier, number of the blocks, size of the blocks, the number
of dies in a row and number of dies in a column. In addition,
initialization information may include the starting point of the
bonding process, such as the starting block and starting die
position within the block, and which die positions are live die
positions and alignment die positions. Other information may
include carrier alignment points in a carrier CAD file and die
alignment points in a die CAD file to facilitate alignment.
At 915, a die is provided to the bonding tool. For example, an
appropriate die (live or alignment die) is provided to the bonding
head unit by a die feeder. The bonding head picks up the die from
the die feeder. After die pickup, the die feeder is retracted to
expose the die region on which the die is to be bonded. For
example, coarse alignment of the die region is performed prior to
die pickup. In other cases, coarse alignment of the die region may
be performed after die pickup. The support alignment assembly
performs fine alignment of the die to the die bonding region at
920. For example, the camera module extends to between the die and
the alignment carrier. Based on the input from the camera module,
the controller aligns the die to the die attach region, both in the
x and y directions as well as the rotational angle.
Once the die is aligned to the die attach region, the camera module
is retracted, enabling the bonding head to move vertically
downwards to place the die on the die attach region of the carrier
at 925. At 930, the die bonder determines if there are more dies to
be bonded. For example, if there are more dies in the block to be
bonded. If yes, the bonding head is translated to the next die
position for bonding at 935. Thereafter, the process repeats from
915 to 930 until the block is completed. If the block is completed,
the process proceeds to 940 to determine whether there are more
blocks on the carrier to be bonded. If there are additional blocks
to be bonded, the process proceeds to 945. The head translates to
the first die position of the next block on the carrier and
proceeds to 915. Thereafter, the process repeats from 915 to 930
until the block is completed. The process continues until all
blocks are processed. Once all blocks have been processed, the
process terminates at 950.
As described, the carrier is configured in multiple blocks.
However, it is understood that the carrier may be configured as a
single block of die bonding regions. In such, the process may be
modified to exclude determining if there are more die blocks.
Furthermore, as described, die bonding is performed for both
alignment dies and live dies. For example, a die bonder loads the
appropriate die for bonding based on the type of die bonding
location until the whole block is bonded and then to the next block
until die bonding of the alignment carrier is completed.
Alternative approaches may be employed for die bonding of an
alignment carrier. For example, alignment dies may be bonded before
bonding live dies using the same die bonder. Alternatively, live
dies may be bonded first followed by bonding the alignment dies. In
other cases, alignment dies and live dies are bonded using
different die bonders. In the case where alignment dies and live
dies are the same dies, they can be all bonded using the same
bonder as well as in the order according to the sequence of die
bond regions.
FIGS. 10a-d show simplified illustrations of an embodiment of an
alignment process 1000. As discussed, the alignment performed by
the die bonder is a local die alignment with a direct or straight
line of sight to the die bonding region on the alignment and to the
die. For example, FIG. 10a depicts the camera module 1050, the die
1014 and the alignment carrier or panel 1010 in alignment position
prior to bonding. For example, the camera module 1050 is disposed
between the die 1014 and the die bonding region 1040 of interest on
the alignment carrier 1010. The camera module utilizes local die
alignment marks 1055 of the die bonding region 1040 for precisely
aligning the die 1014 to the die attach region. As shown, the
bottom surface of the die which is bonded to the carrier is the
active surface. The active surface of the die may be covered by a
transparent dielectric layer, such as an ABT layer. This enables
the lookup camera to view the features of the active surface to
serve as alignment marks. The views of the bottom surface of the
die 1015 and the die region 1040 as captured by the camera unit are
shown in detail. For example, the view of the bottom surface
includes features such as vias 1018 while the view of the die
region includes local die alignment marks 1055 surrounding the die
attach region. In other embodiments, the bottom surface may be the
inactive surface of the die.
FIG. 10b illustrates how alignment is performed. For example,
alignment involves matching a die pattern 1022 of the die 1015 from
the die CAD file and the die region pattern 1062 of the die attach
region 1040 from the carrier CAD file. As shown, the die region
pattern includes features such as alignment marks 1066 and the die
pattern includes features such as vias 1026. In addition, the die
pattern includes die alignment points 1028 and the die region
pattern includes die region alignment points 1068. As shown, the
die alignment points are disposed in a central portion of the die
pattern and the die region alignment points are disposed in a
central portion of the die region pattern. Locating the alignment
marks in other areas of the die pattern and die region pattern may
also be useful. For example, the controller can determine the
offsets as an input to accurately position the die on the target
die bonding region before placement.
As shown in FIG. 10c, the die pattern and the die region pattern
are matched for alignment. For example, the die region pattern is
overlaid on to the die region, with the local die alignment marks
1055 matching the alignment marks of the die region pattern and the
die pattern is overlaid onto the bottom surface of the die, with
the vias 1026 of the die pattern matching the vias 1018 of the die.
Thereafter, the die alignment points 1028 on the die pattern are
then matched to the die region alignment points 1068 of the die
region pattern. This aligns the die to the die region.
Once aligned, the bond head places the die in position on the die
attach region. For example, as shown in the top view 1005a and side
view 1005b in FIG. 10d, dies 1014 are aligned on adjacent die
regions. Furthermore, as shown, adjacent die regions may share
common local die alignment marks 1055 located therebetween. This
further reduces footprint of the die regions, enabling a higher
number of dies to be fitted onto the blocks of the panel.
FIGS. 11a-f show simplified cross-sectional views of an embodiment
of a reconstruction process 1100 of dies using an alignment
carrier. Referring to FIG. 11a, an alignment carrier 1110 is shown.
The alignment carrier includes an active surface 1111 on which a
plurality of die regions 1140 are defined. The active surface, for
example, may be referred to as the front or first surface. The die
regions may be defined according to a carrier CAD file. In one
embodiment, the alignment panel is separated into a plurality of
blocks, each with a plurality of die regions. However, for
simplicity, only two die regions are shown. The active surface of
the alignment carrier includes local die alignment holes or marks
1155. In one embodiment, the local alignment marks surround or are
outside of a die attach region. Other configurations of local
alignment marks may also be useful. For example, the alignment
marks may be within the die attach region or inside and outside of
the die attach region.
As shown, adjacent die regions share common alignment marks. On the
active surface of the alignment carrier, an adhesive tape 1112 is
applied. The adhesive tape covers the die regions, including
alignment marks. The adhesive tape, in one embodiment, is a
transparent adhesive tape, enabling detection of the alignment
marks by a camera module of a die bonder for performing local die
alignment of a die to a die region. Dies 1114 are attached to the
die attach regions. As such, the active surface of the dies are
attached to the carrier. Attaching the inactive surface of the dies
to the carrier may also be useful. The dies are aligned to the die
attach regions of the die regions based on alignment using the
local die alignment marks.
In FIG. 11b, the carrier with bonded dies is subjected to a molding
process. For example, a mold compound 1170 is formed over the
alignment carrier, covering it and the dies. The mold compound and
dies may be referred to as a mold panel while the mold panel on the
carrier may be referred to as a panel assembly. The mold compound
may be in the form of powder/granules, liquid or film. In one
embodiment, compression molding is performed to form the mold
compound. Other techniques for forming the mold compound may also
be useful. The molding process is a high-temperature process. For
example, the alignment panel is subjected to high temperatures and
pressure, such as about 150-180.degree. C. and 240-320 TF. The
material of the alignment carrier can sustain conditions of the
molding process without distortion, warpage or damage. In addition,
due to the low CTE material of the alignment carrier, minimum
linear variations during temperature changes occur. After the mold
compound is formed, the top surface is grounded. For example, the
top surface of the panel is grounded using a grinding wheel 1180,
such as a resin bonding grinding wheel and polishing tool, as shown
in FIG. 11c. For example, the top surface is grounded to the
desired height and ensuring a uniform thickness as well as
relieving stress.
As discussed, the dies may be attached to the alignment carrier
face up (inactive surface attached to the carrier) or face down
(active surface attached to the alignment carrier). In the case of
a face down bonding, the mold compound covers the inactive sides of
the dies attached to the alignment carrier. In such cases, the
desired height of the panel may be any height, including exposing
the inactive surfaces of the dies. In the case of face up bonding,
the grinding exposes the active surfaces of the dies.
As shown in FIG. 11d, the adhesive tape 1112 is released from the
alignment carrier 1110. For example, a release process is performed
to separate the alignment carrier from the adhesive tape 1112. In
one embodiment, the release process includes subjecting the
alignment carrier to a high-temperature process, such as about
210.degree. C. Once the alignment carrier is released from the
adhesive tape, it is peeled off from the mold panel 1160, as shown
in FIG. 11e. This results in the mold panel 1160 with the active
surface of the dies exposed.
In FIG. 11f, the mold panel 1160 is transferred to a carrier
substrate 1190, forming a second mold panel assembly. For example,
an adhesive tape 1192 is provided on the carrier substrate,
enabling the mold panel to attach to the carrier substrate. The
active surfaces of the dies of the mold panel is exposed. The
carrier substrate facilitates handling of the mold panel, such as
transportation to downstream processes. In one embodiment, the
carrier substrate may be similar to the alignment carrier. Using a
carrier substrate which is different from the alignment carrier may
also be useful.
FIGS. 12a-c show an embodiment of a process 1200 for die location
check (DLC) on a carrier substrate. Referring to FIG. 12a, a second
mold panel assembly is shown. For example, the second mold panel
assembly includes a mold panel 1260 attached to a carrier substrate
1220. The mold panel is configured with a plurality of blocks 1230.
A block includes a plurality of dies 1214 arranged in a matrix
format. For example, the dies of a block are arranged in rows and
columns. A block is provided with at least one alignment die 1216
in a designated alignment die region. The number of alignment dies
per block may depend on the DLC scheme used. An alignment die
serves as a reference point for a block.
Illustratively, a block includes 4 alignment dies located at the
corners of the block. For example, each block of the panel includes
4 alignment dies located at the corners of the block. A block may
be provided with other numbers of dies and/or other locations.
Providing four alignment dies facilitates downstream processes. For
purposes of DLC, two alignment dies should be sufficient to
determine the angle of the block. Preferably, the alignment dies
are in the same x or y axis instead of a diagonal. In some cases,
alignment dies may be shared by adjacent blocks.
Referring to FIG. 12b, a die location check scheme is shown. A DLC
scan is performed using multiple cameras. The DLC scans the panel
assembly and identifies the alignment dies of a block. For example,
the alignment dies of each block are identified. As shown, first
and second areas (area A and area B) correspond to first and second
cameras (camera A and camera B) of the DLC scan. The outlines
represent zones scanned by the cameras. For example, the outline of
area A represents zones scanned by camera A and the outline of area
B represents zones scanned by camera B. As shown, zones 1251a
scanned by camera A covers blocks 1 and 3 while zones 1251b scanned
by camera B covers blocks 2 and 4. The alignment dies are used to
determine the origin for a block. For example, one of the alignment
dies serves as an origin die 1216 of a block.
In FIG. 12c, as shown, the alignment die 1216 serves as an origin
die for block 1214 (e.g., block 2). A portion 1247 of block 2
containing the origin die 1216 is shown in greater detail. For
example, the origin die is used to determine the (0, 0) coordinate
of block 2. For example, the 0 or origin point in the x axis and
the 0 or origin point for the y axis are determined from the origin
die. A die is referenced by at least one reference point. In one
embodiment, a die is referenced by two reference points
1230.sub.1-2. Using two reference points facilitates determining
the angular position of a die. In one embodiment, an adjacent
alignment die of the origin die is measured. The two adjacent
alignment dies are used to determine an axis representing the block
orthogonality. As shown, the two alignment dies are used to
determine an x-axis. In other cases, the two alignment dies may be
used to determine a y-axis. Once an axis of block 2 is determined,
the system generates the X, Y coordinates of all die locations of
block 2. In one embodiment, a die is referenced using two reference
points. Using two reference points facilitates determining the
angular position of a die. The die locations of all blocks are
calculated based on an origin die of the respective block. The
results are generated block-by-block, with each block having its
own origin and die coordinate data. In an alternative embodiment,
the coordinates of all die locations of a block are generated based
only on the origin die. For example, the axis representing block
orthogonality is not determined.
In one embodiment, a DLC export file is created. The DLC export
file contains the X, Y coordinates of all die locations of all
blocks of the alignment panel. A die location is represented by at
least one reference point. A reference point corresponds to a set
of X, Y coordinates. In one embodiment, a die location is
represented by two reference points. For example, a die location
corresponds to two sets of X, Y coordinates. The DLC export file,
for example, may be in a CSV format, as shown in FIG. 12d. By
reducing the panel into smaller blocks or segments, higher bonding
accuracy is achieved.
An advantage of the present DLC process, as described, is that it
can generate alignment die as well as live die positions. Live die
positions of the different blocks can be calculated based on the
origin alignment die of a block, with or without block
orthogonality being taken into account. In addition, saw lines 1283
can be calculated, as shown in FIG. 12e. The saw lines can be
calculated by averaging the position of all the die in a row or
column.
FIGS. 13a-e show simplified cross-sectional views of an embodiment
of downstream processing 1300 of dies on a second panel assembly.
Referring to FIG. 13a, a carrier substrate 1390 mounted with a mold
panel 1360 is shown. For example, a second panel assembly is shown.
The mold panel includes dies encapsulated with a mold compound
1370. The mold panel is attached to the carrier substrate by an
adhesive tape 1392, forming a downstream workpiece. Types of
adhesive tapes, such as thermal release tape, may be used to
facilitate die bonding. In one embodiment, a bottom surface of the
mold panel is attached to the carrier substrate. This top surface
of the mold panel includes exposed active surface of the dies 1314
and 1316. The exposed active die surfaces include via openings
which expose bond pads.
The mold panel may be configured with a plurality of blocks. A
block includes a plurality of dies arranged in a matrix format. For
example, the dies of a block are arranged in rows and columns. In
one embodiment, a block is provided with at least one alignment die
1316 in a designated alignment die region. The number of alignment
dies per block may depend on the DLC scheme used. An alignment die
serves as a reference point for a block.
For simplification, the cross-sectional view may depict a simple
block having a 4.times.4 matrix of dies. The block includes
alignment dies 1316 disposed at corners thereof and normal dies
1314 disposed in remaining die locations. It is understood that the
mold panel may include multiple blocks and that a block may include
a much larger sized matrix of dies that have more than than a
4.times.4 matrix.
A DLC scan is performed on the downstream workpiece using a camera
module 1398. The camera module may be configured with multiple
cameras for identifying the alignment dies. The scan is configured
to scan the whole mold panel and generate a map of the die
locations based on the origin points on the mold panel. The system
generates the X, Y coordinates of all die locations with respect to
the origin dies for the mold panel. A DLC export file is created
which contains the X, Y coordinates or map of all die locations of
the mold panel on the carrier substrate.
Referring to FIG. 13b, the DLC export file is sent to a downstream
processing tool for processing. In one embodiment, the processing
may include forming interconnects. In one embodiment, the
downstream processing includes forming an interconnect layer 1375.
The interconnect layer, for example, may be a copper-based alloy,
such as copper titanium. Other types of interconnect or metal
layers may also be useful. The interconnect, for example, is formed
by sputtering, filling the via openings in the dies as well as
covering the surface of the mold panel.
The export DLC file is fed into an laser direct imaging (LDI)
system for patterning the dielectric layer. In one embodiment, the
DLC file is converted into a circuit file readable by the LDI
system. The converted circuit file is used by the LDI system which
takes reference from the alignment dies and extracts the DLC data
for determining the actual die location for patterning the
dielectric layer 1380, so as to form openings 1382 to expose the
filled vias, as shown in FIG. 13c, forming trace areas for trace
interconnects.
Referring to FIG. 13d, the downstream workpiece is subjected to a
plating process. For example, a plating process, such as
electroplating, forms trace interconnects 1378 in the openings of
the dielectric layer. After forming the trace interconnects, the
dielectric layer is removed, as shown in FIG. 13e. Removal of the
dielectric layer may be achieved by, for example, stripping. Other
techniques for removing the dielectric layer may also be useful.
Subsequent processes may include carrier substrate removal and
dicing the panel to singulate the devices.
FIGS. 14a-b show simplified side and top views 1400 of trace
interconnect tolerance with respect to bond contacts of the
downstream processing using the alignment panel with local die
alignment marks and alignment dies. Referring to FIGS. 14a-b, trace
interconnects of a single-die configuration 1405a and a
multiple-die configuration 1405b are shown. For example, the
single-die configuration shows a die 1414 encapsulated by the mold
compound 1470. As for the multiple-die configuration, it
exemplarily shows first and second dies 1414.sub.1 and 1414.sub.2
encapsulated by mold compound 1470. The active surface of the die
or dies includes trace interconnects 1477 disposed over the bond
contacts 1475 filling bond vias which expose the bond pads. As
shown, due to the accurate calculation of the die location based on
the use of local die alignment marks on the alignment carrier and
alignment dies, downstream processing, such as forming trace
interconnects, is more precise. For example, annular ring tolerance
(AR) is +/-10 um. Furthermore, the DLC can further enhance annular
ring tolerance to less than +/-5 um.
As described, die bonding is performed using an alignment carrier
with local alignment marks for improved accuracy. The local
alignment marks may also be applicable for wafer level packaging
(WLP) processes. For example, local alignment marks may be provided
on the dies of a wafer to enhance bonding accuracy.
The present disclosure may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The foregoing embodiments, therefore, are to be considered
in all respects illustrative rather than limiting the invention
described herein. The scope of the invention is thus indicated by
the appended claims, rather than by the foregoing description, and
all changes that come within the meaning and range of equivalency
of the claims are intended to be embraced therein.
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